Have 1988 iroc z convertible that all of a sudden decided to only blow air from the defrost vents no matter where the controls are set. someone told me to check the vacuum lines but after looking in the manual i have no idea which one it could be or if that is even it. any ideas on where i should look. My wife loves the convertible but enjoys a/c when it is really hot outside.

 

Mine did that when I bought it. All i did was plug in a vaccum line back in, it was kind of behind the sterio just laying there. Its worked fine ever since. About 4 years ago.

 

the line for the controls is a thin hard plastic black line. is the car TPI or TBI? If its TPI it plugs in the passenger rear side of the plenum. It runs from the intake and enters the car through the firewall with the rest of the A/C wiring by the underhood A/C box.

 

I have this issue also. My car is a TBI. Can you please explain where the Vacuum line is inside the car and under the hood. Just would like to check both thanks

 

The lines under the hood are just behind the passanger side head, a few inches down. There are two hard plastic lines that come out. The one you want should go to a check valve that is also a T. One side goes to the vacuum orb/canister and the other to the intake/plenum.